An inspection method according to the embodiments includes applying light of a light source to an inspection target; receiving light from the inspection target to obtain a first image of the inspection target by a sensor; based on an image of a first pattern comprising repetitive patterns unresolvable with a wavelength of the light source in the first image, calculating a deviation of luminance values with respect to each of first regions in the first pattern by a processor; obtaining a second image of the inspection target by the sensor; correcting luminance values of the second image by the processor based on the deviations of the luminance values; and comparing the repetitive patterns of the corrected second image with each other by a comparer.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An inspection method comprising: applying light of a light source to an inspection target; receiving light from the inspection target to obtain a first image of the inspection target by a sensor; based on an image of a first pattern comprising repetitive patterns unresolvable with a wavelength of the light source in the first image, calculating a deviation of luminance values with respect to each of first regions in the first pattern by a processor before comparing the repetitive patterns in the image; obtaining a second image of a same area in the inspection target by the sensor, again; correcting luminance values of the second image by the processor based on the deviations of the luminance values; and comparing the repetitive patterns of the corrected second image with each other by a comparer.
2. The method of claim 1 , wherein the deviation of the luminance values of each of the first regions is a difference between a luminance average value of each of the first regions in the first image and a luminance average value of the first pattern in the first image.
3. The method of claim 1 , wherein correcting luminance values of the second image is subtracting deviations of luminance values of the first pattern from luminance values of the first pattern in the second image.
4. The method of claim 1 , further comprising: calculating correction values by inverting signs of deviations of luminance values in the first pattern, wherein correcting luminance values of the second image is adding the correction values to luminance values of the first pattern in the second image.
5. The method of claim 1 , wherein the first image comprises the first pattern and a second pattern resolvable with the light of the light source, and deviations of luminance values in the first pattern are calculated after extracting luminance values of the first pattern from the first image or eliminating the second pattern from the first image.
6. The method of claim 5 , wherein the first and second patterns comprise second regions arranged to be periodically repeated, and in comparing the repetitive patterns with each other, comparison of each of the first and second patterns is performed with respect to each of the second regions, comparison of the first pattern is performed using the second image corrected, and comparison of the second pattern is performed using the second image uncorrected.
7. The method of claim 1 , further comprising: comparing between luminance of a first repetitive pattern and luminance of a second repetitive pattern in the second image corrected, and determining that the inspection target has a defect when a luminance difference between the first repetitive pattern and the second repetitive pattern or a differential value of the luminance difference is larger than a first threshold.
8. The method of claim 1 , wherein a size of the first regions is smaller than that of the repetitive patterns and larger than that of pixels of the sensor.
9. The method of claim 1 , wherein the inspection target is determined to have a defect, luminance values of the second image are not corrected, and the repetitive patterns are not compared when the deviations of the luminance values are larger than a second threshold.
10. The method of claim 1 , wherein a pixel size of the first Image is larger than that of the second image.
11. An inspection apparatus comprising: an optical system applying light to an inspection target; an image sensor receiving light from the inspection target to obtain an image of the inspection target; a processor calculating, based on a first image of a first pattern comprising repetitive patterns unresolvable with a wavelength of a light source of the optical system in the image of the inspection target, a deviation of luminance values with respect to each of first regions in the first pattern before comparing the repetitive patterns in the image, the processor correcting luminance values of a second image of the inspection target based on the deviations of the luminance values, the second image being an image of a same area in the inspection target; and a comparer comparing the repetitive patterns of the corrected second image with each other.
12. The apparatus of claim 11 , wherein the deviation of the luminance values of each of the first regions is a difference between a luminance average value calculated for each of the first regions and a luminance average value of the first pattern in the first image.
13. The apparatus of claim 11 , wherein correcting luminance values of the second image of the inspection target is subtracting deviations of luminance values of the first pattern from luminance values of the first pattern in the second image of the inspection target, or adding correction values obtained by inverting signs of the deviations of the luminance values of the first pattern to the luminance values of the first pattern in the second image.
14. The apparatus of claim 11 , wherein further comprising: a storage storing therein deviations of luminance values of the first pattern or correction values obtained by inverting signs of the deviations of the luminance values of the first pattern along with positional information.
15. The apparatus of claim 11 , wherein the first image of the inspection target comprises the first pattern and a second pattern resolvable with the light of the light source, and the processor calculates deviations of luminance values in the first pattern after extracting luminance values of the first pattern from the first image of the inspection target or eliminating the second pattern from the first image of the inspection target.
16. The apparatus of claim 11 , wherein the processor and the comparer do not correct the luminance values of the second image of the inspection target, determine that the inspection target has a defect, and do not compare the repetitive patterns when the deviations of the luminance values are larger than a second threshold.
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May 25, 2017
March 24, 2020
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